1. Field of the Invention
This invention is directed to a method and a system for measuring voltage and current levels using an Integrated (i.e. in-line) Voltage and Current (VI) Probe.
2. Discussion of the Background
In the fabrication and processing of semi-conductor wafers, such as silicon wafers, a variety of different semiconductor equipment and processes can be utilized. For example, wafer processing techniques are known in the art and may include, for example, photolithography, ion beam deposition, vapor deposition, etching, as well as a variety of other processes.
In one method of wafer processing, plasma generators are used to process a wafer, for example by etching a layer formed on the surface of the wafer. In employing this technique, electrical power is coupled to the plasma generator from an electrical source. Typically, the electrical energy has a frequency in the radio frequency (RF) range. Control of the process is performed in part by measuring and monitoring the RF signal. The power input into the system can be determined by measuring the RF voltage (V) and the current (I) components of the RF power source coupled to the plasma generator. Thus, a common practice for measuring RF power is to install a sensor for monitoring current and voltage in series with the transmission medium coupling the RF power to the plasma generator.
Sometimes, however, the presence of the RF probes can itself disrupt the propagating electro-magnetic fields the probes are intended to measure. This may occur through reflections of the RF signal, for example, that are imposed by the implementation of the RF probe(s). Consequently, there exists a need for an integrated voltage and current probe to monitor a source of RF electrical power which minimally intrudes in the RF transmission line in which the probes are placed.
Moreover, the presence of RF probes can affect proven processes, which is entirely unacceptable to device manufacturers. As the probes are installed in the RF transmission structure outside the chamber and sometimes beyond the output of the match network, the above-identified problem can be further exacerbated when commercially available probes are utilized. Therefore, there exists a need for an integrated voltage and current probe to monitor a source of RF electrical power, which minimally affects a proven process.